1. Field of the Invention
The present invention relates to a device which uses voice recognition to search for various texts such as a document.
2. Description of the Related Art
As a technique of searching for various texts such as a document by using a voice, a method of using dictation voice recognition to convert a voice into a text to make a full-text search on a text is common. According to this method, however, the number of recognizable words is limited to several thousands to several tens of thousands. Therefore, if a document containing words, which are out of the range of recognizable words, is to be found by a search, it is necessary to take the presence of unknown words into consideration.
In order to cope with the above-described problem, Japanese Patent Application Laid-open No. 2003-271629 discloses the following technique. In a document to be found by a search, only the top K words, which are the most frequently appearing words, are recognized as words, whereas the other words are recognized in units of syllables. Then, a full-text search is made by using the words extracted as the results of recognition to preliminarily select a document. Thereafter, the part recognized as a syllable string is estimated as a word to obtain a final result of the search.
In the above-described related art, the full-text search is performed using the words as index words for the parts recognized as words contained in an input voice. Therefore, if any of the parts recognized as the words is falsely recognized, a search precision is disadvantageously lowered. For example, even if a speech is “wakayamanonachiotaki” and the result of recognition is fully obtained as words as “okayama no machi otaku”, a document containing “wakayamanonachiotaki” cannot be found by the search.